1. Field of the Invention
The present invention relates to a method for manufacturing a substrate provided with a semiconductor layer with an insulating film interposed therebetween, especially, a silicon-on-insulator (SOI) substrate. The present invention also relates to a method for manufacturing a semiconductor device using a substrate provided with a semiconductor layer with an insulating film interposed therebetween.
2. Description of the Related Art
In recent years, integrated circuits have been developed which use a silicon-on-insulator (SOI) substrate in which a thin single crystal semiconductor layer is present over an insulating surface, instead of a bulk silicon wafer. The use of an SOI substrate can reduce parasitic capacitance between a drain of a transistor and a substrate; thus, SOI substrates are attracting attention for their ability to improve performance of semiconductor integrated circuits.
One of known methods for manufacturing SOI substrates is a Smart Cut (registered trademark) method (for example, see Patent Document 1). A summary of a method for manufacturing an SOI substrate by a Smart Cut method is described below. First, hydrogen ions are implanted into a silicon wafer by an ion implantation method to form an embrittled region at a predetermined depth from a surface. Next, the silicon wafer into which hydrogen ions have been implanted is bonded to another silicon wafer with a silicon oxide film interposed therebetween. Then, by heat treatment, a part of the silicon wafer into which hydrogen ions have been implanted is separated in a thin film shape along the embrittled region. Accordingly, a single crystal silicon film can be formed over the other bonded silicon wafer. Moreover, the Smart Cut method is also referred to as a “hydrogen ion implantation separation method”.
Further, a method for forming a single crystal silicon layer over a base substrate made from glass by using such a Smart Cut method as described above has been proposed (for example, see Patent Document 2). Glass substrates can be manufactured in larger sizes and are less expensive than silicon wafers. Thus, glass substrates are mainly used for manufacturing liquid crystal display devices and the like. The use of a glass substrate as a base substrate makes it possible to manufacture a large-sized inexpensive SOI substrate.